1. Field of the Invention
The equimolecular salt of piperazine and 1,2-diphenyl-4-butyl-3,5-dioxo pyrazolidine of the following formula ##STR1## is a known compound which is used as a pharmaceutical compound for the treatment of rheumatic diseases.
This invention relates to an improved method or process for preparing said salt of formula I.
2. Description of Prior Art
According to a known method for preparing said salt of formula I, anhydrous piperazine is dissolved in acetone, the obtained solution is poured into a solution of the pyrazolidine derivative also in acetone, the obtained mixture is poured into hexane, wherein the desired salt precipitates, said precipitate being finally separated by filtration and dried.
In a particular embodiment of said known method 17,4 g of anhydrous piperazine (0.2 mole; excess of 100%) are dissolved in 550 ml of acetone and the obtained solution is poured into a solution of 30.8 g (0.1 mole) of the pyrazolidine derivative in 550 ml of acetone, the obtained mixture being then poured into 1100 mol of hexane, 32 g of the desired salt are obtained.
The yield of the desired salt, when the known method is used, is about 80-82 percent.